A Spectroscopic Study of Solid-density HED Plasmas Isochorically Heated by X-ray FEL beam

The behavior of solid-density plasma in the high energy density (HED) regime is important for the study of stellar matter and inertial confinement fusion, yet many phenomena, such as nonlinear transport, partial ionization, strong coupling, and atomic processes, are poorly understood under such HED conditions. With the advent of the X-ray free-electron lasers (XFEL), intense x-ray radiation, in excess of 10¹⁷ W/cm² at X-ray photon energies, can be applied to samples to create and probe such HED matter, under well-defined conditions. While HED states at temperatures around 180 eV have been successfully created in low Z materials, using soft X-rays at LCLS [1-3], the isochoric heating of solid-density plasmas to temperatures at higher temperatures, approaching the 100’s eV region in mid and high-Z system, remains elusive; this requires X-ray intensities above 10¹⁸ W/cm². Here we report applying intense 9 keV X-ray photon energy to 2 or 10 μm thick 3d transition metals. We systematically investigated K_α and K_β emissions, and influence of the continuum at various Z-elements between Cr (Z=24) and Zn (Z=30) using LiF and HAPG spectrometers. Satellite K_α emissions, with respect to the cold K_α emissions predicted using the Hartree-Fock code, will be discussed for different charge states and Z. In addition, the evolution of K_β satellites will be presented.